Internet protocol (IP) multimedia subsystem (IMS) is defined by the Third Generation Partnership Project (3GPP) as a mobile network infrastructure that enables the convergence of data, speech, and mobile network technology over an IP-based infrastructure. IMS bridges the gap between the existing traditional telecommunications technology and Internet technology, allowing network operators to offer a standardized, reusable platform with new, innovative services by enhancing real time, multimedia mobile services, such as voice services, video telephony, messaging, conferencing, and push services. IMS can be used to provide services for both mobile networks and fixed networks at the same time, providing unique mixtures of services with transparency to the end-user.
IMS supports the establishment of any type of media session (e.g., voice, video, text, etc.) and provides the service creator the ability to combine services in the same session and dynamically modify sessions (e.g., adding a video component to an existing voice session). As a result, new and innovative user-to-user and multi-user services have become available, such as enhanced voice services, video telephony, chat, push-to-talk, and multimedia conferencing, all of which are based on the concept of a multimedia session. The underlying IMS infrastructure enables mobile IP communication services via its ability to find a user in the network and then to establish a session with the user. The key IMS components enabling mobility management are the call session control function (CSCF) and home subscriber server (HSS). The CSCF is essentially a proxy, which aids in the setup and management of sessions and forwards messages between IMS networks. The HSS holds all of the key subscriber information and enables users (or servers) to locate and communicate with other end users.
As the number of subscribers or processing load on an individual HSS increases, it may be desirable for a network operator to include multiple HSSs in a network. If each of the multiple HSSs is identically provisioned, i.e., includes copies of the same subscriber data, the HSSs may operate in a load sharing manner and it is not necessary to have a location function to determine which HSS holds a particular subscriber's data. However, if the multiple HSSs do not include identical data, it is necessary to identify the HSS that contains a particular subscriber's data when attempting to establish a call involving that subscriber. IMS documentation defines a subscriber locator function (SLF) for locating the HSS serving a particular subscriber when the subscriber's network includes multiple HSS functions. However, the implementation of the SLF is not believed to be specified.
Accordingly, there exists a need for improved methods, systems, and computer program products for identifying a serving home subscriber server in a communications network.